Anode for use in aluminum electrolysis having a peg in its head protected by a sleeve



July 1, 1969 K. FRICKER ANODE FOR USE IN ALUMINUM ELECTROLYSIS HAVING A PEG IN ITS HEAD PROTECTED BY A SLEEVE Filed Sept. 26. 1966 PRIQR ART Sheet ofS INVENTOR A7424 Few/r5? 3,453,199 FOR USE IN ALUMINUM ELEGTROLYSIS HAVING A PEG IN ITS HEAD PROTECTED BY A SLEEVE Filed Sept. 26, 1966 July 1, 1969 K'. FRICKER ANODE Sheet 7 INVENTOR: K424 FR/CAEP BY Wm Md We/ ATTORNE s.

y 1, 1969 K. FRICKER 3,453,1

ANODE FOR USE IN ALUMINUM ELECTROLYSIS HAVING A PEG IN ITS HEAD PROTECTED BY A SLEEVE Filed Sept. 26, 1966 Sheet 3 Of 3 INVENTOR 4%? FAP/C/(ER United States Patent 01 ice 3,453,199 ANODE FOR USE IN ALUMINUM ELECTROLYSIS HAVING A PEG IN ITS HEAD PROTECTED BY A SLEEVE Karl Fricker, Meilen, Zurich, Switzerland, assignor to Swiss Aluminium Ltd., Chippis, Switzerland, a jointstock company of Switzerland Filed Sept. 26, 1966, Ser. No. 582,117 Claims priority, application Switzerland, Sept. 30, 1965, 13,522/ 65 Int. Cl. B01k 3/04 US. Cl. 204-286 8 Claims Baked (burnt) carbon anode rod-electrodes or blockelectrodes for the fusion electrolysis of aluminum in a fluoride electrolyte are generally provided with an iron peg which is inserted in the upper part (the head) of the carbon anode electrode and is fixed there by ramming a granular or pasty synthetic carbon composition around it or by pouring in a molten synthetic carbon composition. A carbon anode rod-electrode, for example, ordinarily has a cross-section of about 300 x 300 mm. to 500 x 500 mm. in width and a height of about 400-550 mm. The iron peg is used to connect the electrode to the power supply by clamping.

When the carbon anode electrode has been inserted in the electrolytic furnace, its head becomes heated to about 180 C. After 6 days, the temperaure at this point rises on an average to about 290 C. Because of wear, the carbon anode must be gradually lowered. Finally it is so low that the iron peg also dips into the cryolite melt. The lower end of the peg surrounded by the carbon composition is protected by it, but not that part thereof Which projects from the carbon electrode. So that this part may not scale off and be partly dissolved in the electrolyte, it, also, must be protected. This is achieved, for example, with the aid of a synthetic carbon composition (cokepitch mixture) which is rammed or poured into a socket placed in a recess on the head of the anode. A collar of sheet aluminum (which is hereinafter called a sleeve) is very suitable as a socket, because aluminum that is melted away does not contaminate the bath and is recovered in the cathodic layer of aluminum.

For an iron peg with a cross-section of 100 x 100 mm., for example, a sleeve which is about 170 x 170 mm. in plan and about 100-200 mm. in height is used. The thickness of the sheet metal, for example, is about 1 mm. Hard-rolled pure aluminum sheet, the cleanness and sur face condition of which (scaly, scratched, etc.) are (practically speaking) of no importance, is advantageously used for making the sleeve. It is therefore advantageous to use waste sheet. Of course, alloyed aluminum may also be employed, if it does not contain alloying metals in such quantity as to contaminate the aluminum recovered in the electrolytic cell in an unacceptable manner.

As the iron pegs have a rectangular cross-section, preferably one that is square, sleeves of square or other rec tangular cross-section are used. To this end, the recess in the head of the car-bon anode rod is square or otherwise rectangular and the sleeve fits closely into this recess.

In accordance with the invention, such a sleeve consists of a strip of sheet aluminum which is folded to pro duce a tube of substantially rectangular cross-section with three flat walls, and with the edges of the strip meeting and interlocking part way along the fourth wall, one of the edges being bent to form a first flange projecting inwardly into the rectangle outlining the sleeve, and the other edge being bent to form an inclined portion extending inwardly into this rectangle and at the end of the inclined portion an outwardly extending second flange, the first flange hooking into the outwardly-facing substantially V-shaped groove formed between the inclined portion and the second flange.

3,453,199 Patented July 1, 1969 With this arrangement no part of the interlocking edges of the strip lies outside the rectangular section of the sleeve, and the sleeve can nest easily in a rectangular recess in the head of a carbon anode electrode around its peg.

The invention also comprises sleeve-forming apparatus comprising a former of rectangular section around which a strip of sheet aluminum is arranged to be bent to form the sleeve or tube and which has three smooth faces for forming the three flat walls of the tube and a fourth face formed with a V-shaped groove extending parallel to the edges of the former with the base of the groove adjacent to that face of the former over which the wall of the tube which will carry the part of the fourth wall of the tube on which the first flange is formed, a pressure jaw for clamping the aluminum strip against the middle of the three flat faces of the former, a pair of shaping jaws which are arranged to be swung up so that they each closely embrace a different one of the other two flat faces and part of the grooved face of the former in order to bend the strip which is clamped by the clamping jaw against one flat face of the former along the other two flat faces of the former and over the grooved face of the former, and an element having a folding edge which is arranged to be swung against the grooved face of the former so that the folding edge enters the V-shaped groove and forms the first flange and the inclined portion and second flange on the edges of the strip by forcing them into the groove of the former;

FIG. 1 shows in horizontal cross-section a sleeve of a type on which the present invention is an improvement;

FIG. 2 shows a sleeve according to the invention, like wise in horizontal cross-section;

FIG. 3 illustrates diagrammatically and in longitudinal section an apparatus for producing a sleeve such as shown in FIG. 2;

FIGS. 4, 5, and 6 are diagrammatic views from the view point of FIG. 3 but on smaller scale showing three successive working positions of the shaping tool of the apparatus of FIG. 3; and

FIG. 7 shows a detail portion of FIG. 6 on an enlarged scale.

In a factory of applicants assignee in Switzerland, an aluminum sleeve is being used which is made of a strip of sheet the two ends of which are united by a clasp joint or fold. This sleeve, which is shown in FIG. 1 in horizontal cross-section as it comes from the automatic manufacturing machine, is not the subject of the present invention. The sleeve has an approximately square cross-section, but the wall portion 10 with its inwardly folded end 11 and the outwardly bent edge 12 of the wall portion 13 project from the square plan. The bent edges 11 and 12 must still be beaten or pressed flat, so that a clasp joint may be formed to prevent the sleeve from opening when the synthetic carbon composition is poured in, and to provide the completely square horizontal cross-section enabling the sleeve to be inserted in the square recess in the head of the anode.

The sleeve for protecting the iron peg according to the present invention is likewise made of a strip of sheet aluminum, but is so designed that it does not require a clasp joint and fits closely into a square or other rectangular recess. It is exemplified in FIG. 2, in horizontal crosssection, and has walls 14, 15 and 16 which are flat and unshaped. A fourth wall 17 consists of a wall portion 18 which is folded by from the wall 14 and which itself has an edge flange 19 folded inwardly by, for example, about 90preferably 90 to or (more generally) by an angle between 45 (more specifically 70) and and a part 20 folded by 90 from the wall 16 and bent slightly inwards approximately in the last third of its width and having a flange 21 folded outwards so as to be at an anglepreferably 90 to 100between 45 (more 3 specifically 70) and 130 with the plane of wall 17, and preferably substantially parallel to the flange 19. The flange 21 engages behind the flange 19 in use. Consequently, the wall 17 partially projects inwards, but not outwards.

The width of the part 18 must be at least so large that the flange 21 can engage without any difficulty between the wall 14 and the flange 19. On the other hand, it should be sufliciently small to support the part 20 against yielding to any significant extent under the pressure of the synthetic carbon composition poured in between the iron peg and the sleeve. It is also to be borne in mind that a too narrow wall part 18 makes it diflicult to produce the sleeve by means of the apparatus according to the present invention which is described hereinafter. A width of 15 to 25 mm. (including rounded corners) is very suitable in the case of a sleeve with a crosssection of about 170 x 170 mm. With rigid material, e.g. hard pure sheet aluminum 1 mm. thick, the wall part 18 may be up to about 40 mm. wide in the case of the sleeve in question without any disadvantage. The width of the flange 19, including the rounded corner, is, for example 8 to 10 mm. and that of the flange 21 is about 10 mm. Small tolerances in the dimensions of the walls 14, and 16 are permissible, since we are not concerned with a high-precision apparatus in the present case.

The flanges 19 and 21 must be so shaped that they are held together in the position of use and do not become disengaged from one another without some external effect. The angle which they each form with the other sheet-metal part must be such that this clamping action is ensured in the position of use.

After the synthetic carbon composition has been poured in between the iron peg and the present sleeve, there are no more precautions to be taken with the sleeve.

The supplementary operation of making a clasp joint, necessary with the old FIG. 1 sleeve, is dispensed with when the sleeve according to the present invention is employed, so that expense is saved. In view of the large number of carbon electrodes per furnace and the large series of furnaces, this saving of expense is important. Fractions of cents per kg. are counted in the production of aluminum; every fraction saved has a notable effect in the final balance sheet of a factory.

In certain of its aspects the invention contemplates the provision of apparatus for producing the new sleeve. This apparatus, as exemplified in FIGS. 3 to 6, essentially comprises a pressure-shaping former 22 with shaping surfaces 23, 24, 25 and 26 and shaping edges 27, 28, 29 and 30. It has a recess 31 of approximately V-shaped cross-section in the surface 23, the recess being parallel to the shaping edge 27 and its lowest point being in the vicinity of the edge 27. A pressure jaw 32 can be pressed against the surface 25 which is opposite the surface 23 with the recess 31. Two bending jaws 33 and 34 can be swung in succession about pivots 35 and 36, respectively, and have a free edge offset through 90 with respect to projections 37 and 38, respectively. These bending jaws are arranged on opposite sides of the press-shaping former 22 with their pivotal axes parallel to the length of the recess 31 and can be swung against the surfaces 26 and 24, so that they embrace the edges 27 and 28. The bendign jaw 33, the projection 37 of which is located in the vicinity of the recess 31 during the operation of the apparatus, is arranged to be swung first. An element 39 equipped with a sharp folding edge 40 can swing about a pivot spindle 41 into a position in which its folding edge 40 engages in the recess 31. Driving and control means known per se are provided for actuating the pressure jaw 32, the bending jaws 33 and 34, and the element 39, as well as for ejecting the sleeve.

Of course, the width of the surfaces 23, 24, 25 and 26, the bending jaws 33 and 34 and the edge 40 is related to the width of the sheet metal to be worked, that is the height of the sleeve to be produced.

The apparatus is preferably set up with the former 22 directed upwards, but it could also be used in any other desired position.

In FIGS. 3 to 6 it is assumed that the apparatus is in the preferred position, with the former 22 directed upwards. The sheet aluminum is unwound from a reel in the form of a strip 42 which, for example, is about 200 mm. wide and about 1 mm. thick by means of rolls serving as a conveying device and is introduced into the gap between the former 22 and the pressure jaw 32, pushed forward until it is in the vicinity of the free end of the bending jaw 33 and cut to the required length. The sheet metal is indicated in FIGS. 3 to 6 in chaindotted lines. The former 22 has on the side where the surface 23 is located, along the recess 31, a marginal surface 43 which preferably slopes slightly downwards; this slope is provided to take into consideration the springing back of the folded sheet metal. After ejection, the marginal part 18 (FIG. 7) should form a right angle with the wall 14. The side wall 44 of the recess 31 is at an angle of about 90, preferably somewhat less (up to about 80), to the marginal surface 43. The side wall 45 of the recess 31 forms in turn an obtuse angle of, for example, to with the surface 23 of the former. The groove 46 is advantageous, because it receives small portions of material by which the required length of the piece of sheet metal cut to size is exceeded, but it is not absolutely essential. The length of the strip 42 emerging between the former 22 and the pressure jaw 32 should be such that the strip can be bent around the edges 30 and 27 onto the surface 44 (FIG. 3) and form the flange 19 (FIG. 7) at this point. A limit switch (not shown) is arranged at the point of furthest advance of the sheetmetal strip 42 and, on contact with the sheet metal 42, stops the conveying device by transmitting a pulse. At the same time, the sheet metal is clamped upwardly against the former 22 from below by the pressure jaw 32 and the shears, which are likewise not shown, are operated and cut the sheet metal from the strip to the required length. That part of the piece of sheet metal cut to size which projects beyond the bending jaw 34 must be of such length, that, after being bent round the edges 29 and 28, it extends as far as the marginal surface 43, covers at this point the other end of the piece of sheet metal cut to size, which end is bent round the edge 27, and can form the flange 21 (FIG. 7) under the effect of the pointed folding member 40.

The bending operation begins simultaneously with the cutting off or immediately thereafter, by the bending jaw 33 comprising the projection 37 bending one part of the piece of sheet metal cut to size round the edges 30 and 27. The position reached is shown in FIG. 4. As can be seen, the edge 47 of the sheet metal projects horizontally beyond the inner edge 49 of the surface 43 approximately as far as the middle of the recess 31. Shortly thereafter, the longer part of the piece of sheet metal cut to size is bent round the edges 29 and 28 of the former 22 by the bending jaw 34 comprising the long projection 38, so that after this operation has been carried out the two ends of the sheet metal are located over the recess 31, as shown in FIG. 5. It is apparent from this that after this operation the edge 48 of the sheet metal covers the edge 47 to beyond the edge 49.

It is furthermore apparent from FIG. 5 that, the rightangled projection 37 of the bending jaw 33 extends only so far over the surface 43 that it does not interfere with the placing of the edge 48 on the edge 47 by the bending jaw 34. The projection 38 does not need to be longer than the projection 37, because its function is to bend the piece of sheet metal cut to size round the edge 28 through 90. In the illustrated example, however, it is considerably longer, so that the sheet metal is guided over a longer distance after being bent round the edge 28 and its edge 48 rests satisfactorily on the edge 47 when, during the next operation, the sharp edge 40 forces the two edges lying one on the other into the recess 31.

In the position according to FIG. 5, the transmission of a pulse for the bending element 39 takes place by way of a limit switch and the bending element forces the two free ends 47 and 48 of the cut piece of sheet metal into the groove by means of the edge 40, as a result of which the final position according to FIG. 6 is reached. In this figure, the folded flanges 19 and 21 of the sleeve as shown in FIG. 2 can be seen.

The sleeve is now finished. The bending jaws and the element 39 are swung back, the pressure jaw 32 is lowered and the sleeve is ejected automatically.

Of particularly great importance in the apparatus according to the present invention are the recess 31 in the former 22 and the pointed folding member of the element 39, the co-operation of which produces the folding of the free ends of the cut piece of sheet metal in the required manner in a single operation, the flanges 19 and 21 being formed.

When the sleeve ejected from the apparatus according to the present invention is employed, it is opened at the flanges 19 and 21 and placed round the iron peg of the carbon anode rod, whereupon the flange 21 is made to engage behind the flange 19 and the sleeve is inserted in the square recess in the head of the carbon anode rod.

What is claimed is:

1. A carbon anode electrode for use in the fusion electrolysis of aluminum and having in its head an electrically conducting peg, wherein the peg is surrounded by a sleeve consisting of a strip of sheet aluminum which is folded to produce a tube of substantially rectangular cross-section with three flat walls and with the edges of the strip meeting and interlocking part way along the fourth wall, one of the edges being bent to form a first flange projecting inwardly and the other edge being bent to form an inwardly inclined portion having at its end an outwardly extending second flange, the first flange hooking into the outwardly facing groove formed by the inclined portion and the second flange.

2. Apparatus according to claim 1, in which the first flange is folded between about and 130 from the plane of the fourth wall and the second flange is bent so as to be at an angle of about 45 to 130 with the plane of the fourth wall.

3. Apparatus according to claim 2, in which the first flange is at an angle of from about to about 130 from the plane of the fourth wall and the second flange is substantially parallel thereto.

4. Apparatus according to claim 3, in which the first flange is folded back at an angle of from to 5. Apparatus according to claim 1 which has a substantially square cross-section.

6. Apparatus according to claim 1, in which the part of the fourth wall carrying the second flange is wider than the part of the fourth wall carrying the first flange.

7. Apparatus according to claim 6 which has a substantially square cross section with a side of approximately mm. and wherein the width of the part of the fourth wall carrying the first flange is at most 40 mm.

8. Apparatus according to claim 7 wherein the width of the part of the fourth wall carrying the first flange is between 15 and 25 mm.

References Cited UNITED STATES PATENTS 5/1930 Westly 204-294 10/1962 Haupin et al 204-290 us. 01. X.R. 204-290, 294 

1. A CARBON ANODE ELECTRODE FOR USE IN THE FUSION ELECTROLYSIS OF ALUMINUM AND HAVING IN ITS HEAD AN ELECTRICALLY CONDUCTING PEG, WHEREIN THE PEG IS SURROUNDED BY A SLEEVE CONSISTING OF A STRIP OF SHEET ALUMINUM WHICH IS FOLDED TO PRODUCE A TUBE OF SUBSTANTIALLY RECTANGULAR CROSS-SECTION WITH THREE FLAT WALLS AND WITH THE EDGES OF THE STRIP MEETING AND INTERLOCKING PART WAY ALONG THE FOURTH WALL, ONE OF THE EDGES BEING BENT TO FORM A FIRST FLANGE PROJECTING INWARDLY AND THE OTHER EDGE BEING BENT TO FORM AN INWARDLY INCLINED PORTION HAVING AT ITS END AN OUTWARDLY EXTENDING SECOND FLANGE, THE FIRST FLANGE HOOKING INTO THE OUTWARDLY FACING GROOVE FORMED BY THE INCLINED PORTION AND THE SECOND FLANGE. 